Corda node_transaction table column transaction_value

Question

While browsing through the node_transaction table in PostgreSQL, I could see the transaction_value column defined as oid, and the value stored in the column has a length of 6 or 7. In H2, the value stored in the transaction_value column is more. The Corda documentation says transaction_value stores the binary representation of the transaction. So in the case of PostgreSQL, where exactly is the transaction value stored, and how is it related to the oid type?